The recent discovery that the massive elliptical galaxy NGC 1277, located in the Perseus cluster, has less than 5% dark matter within five effective radii has motivated questions about whether such an object can form in a ΛCDM universe. Ana Contreras-Santos and colleagues demonstrate the existence of comparable dark matter deficient satellite ellipticals in simulations, and chart their evolutionary histories to determine the physical processes driving their lack of dark matter in the present day.

The authors present as case studies the two most dark matter deficient elliptical galaxies (M_⋆/M_tot ~ 0.85, M_⋆ ~ 10¹¹ M_⊙) in The Three Hundred Project simulation. They find that both start out with much more massive dark matter halos which are tidally stripped by approximately 2 orders of magnitude upon infall into their clusters, whilst the stellar mass stays largely intact due to its much tighter central concentration. Contreras-Santos et al. then show that the most dark matter deficient systems generally tend to have completed an exceptionally high number of orbits around their host and have reached closer pericentric distances. This creates a picture in which dark matter stripping increases in proportion to how close a galaxy gets to the cluster centre and how long it spends there — meaning that the same mechanism that strips low-mass dwarf galaxies can be effective in massive ellipticals as well.

最近发现，位于英仙座星系团的大质量椭圆星系 NGC 1277 在五个有效半径内的暗物质含量不到 5%，这引发了人们对这种天体是否可以在 ΛCDM 宇宙中形成的疑问。Ana Contreras-Santos 及其同事在模拟中证明了存在类似的暗物质缺陷卫星椭圆，并绘制了它们的进化历史，以确定导致它们当今缺乏暗物质的物理过程。

作者以案例研究的形式介绍了 The Three Hundred Project 模拟中的两个最缺乏暗物质的椭圆星系（M_⋆/M_tot ~ 0.85， M_⋆ ~ 10¹¹M_⊙）。他们发现，这两个星系团开始时都是质量更大的暗物质晕，这些暗物质晕在落入它们的星团时被潮汐剥离了大约 2 个数量级，而由于其更紧密的中心集中，恒星质量基本保持完整。Contreras-Santos 等人随后表明，最暗物质缺陷的系统通常倾向于围绕其宿主完成异常多的轨道，并达到更近的心周距离。这就形成了这样一幅图画：暗物质剥离的增加与星系团离星系团中心的距离和在那里停留的时间成正比——这意味着剥离低质量矮星系的相同机制在大质量椭圆星系中也可以有效。